On Thu, 2015-02-19 at 17:05 +0200, Mathias Nyman wrote:
> On 19.02.2015 02:34, Tim Chen wrote:
> >
> > Commit d92ef66c4f8f ("x86: make dma_alloc_coherent() return zeroed memory
> > if CMA is enabled") changed the dma_alloc_coherent page clearance from
> > using an __GFP_ZERO in page allocation to not setting the flag but doing
> > an explicit memory clear at the end.
> >
> > However the memory clear only covered the memory size that
> > was requested, but may not be up to the full extent of the
> > last page, if the total pages returned exceed the
> > memory size requested. This behavior has caused problem with XHCI
> > and caused it to hang:
> >
> > kernel: xhci_hcd 0000:00:14.0: Stopped the command ring failed, maybe the
> > host is dead
> > kernel: xhci_hcd 0000:00:14.0: Abort command ring failed
> > kernel: xhci_hcd 0000:00:14.0: HC died; cleaning up
> > kernel: xhci_hcd 0000:00:14.0: Error while assigning device slot ID
> > kernel: xhci_hcd 0000:00:14.0: Max number of devices this xHCI host
> > supports is 64.
> >
> > This patch reverts xhci the use the old behavior to avoid the hang. XHCI
> > should
> > do a proper fix to avoid this un-allocated memory.
> >
> > Signed-off-by: Tim Chen <tim.c.c...@linux.intel.com>
> > Cc: <sta...@vger.kernel.org> # 3.16+
> > ---
> > drivers/usb/host/xhci-mem.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> > index 5cb3d7a..39e7196 100644
> > --- a/drivers/usb/host/xhci-mem.c
> > +++ b/drivers/usb/host/xhci-mem.c
> > @@ -1658,7 +1658,7 @@ static int scratchpad_alloc(struct xhci_hcd *xhci,
> > gfp_t flags)
> > goto fail_sp;
> >
> > xhci->scratchpad->sp_array = dma_alloc_coherent(dev,
> > - num_sp * sizeof(u64),
> > + PAGE_ALIGN(num_sp * sizeof(u64)),
> > &xhci->scratchpad->sp_dma, flags);
> > if (!xhci->scratchpad->sp_array)
> > goto fail_sp2;
> >
>
> Thanks for figuring out that the issue was in allocation of scratchpad memory.
>
> Turns out we don't calculate the num_sp correctly in the first place, we
> didn't include
> the additional high order field of the max scratchpad buffers xhci tells we
> should reserve.
> I got a patch for this and will send it to forward to Greg once 3.20-rc1 is
> tagged
>
> -Mathias
Great. Thanks for fixing this.
Tim
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